Process for removing copper deposits from surfaces

ABSTRACT

Copper deposits are removed from a ferrous metal surface by circulating an aqueous acidic solution containing an hydroxy carboxylic acid and/or one of its acidic salts into contact with the surface, regenerating the spent acid solution by contacting it with an immiscible liquid which preferentially extracts copper dissolved in the solution, and recontacting the surface with the regenerated acid solution. Subsituted hydroxy benzophenoximes and/or Alpha -hydroxy oximes are used as the immiscible extraction liquid.

Uit atent 1 Dec. 110, 1974 [22] Filed:

Smith PROCESS FOR REMOVING COPPER DEPOSITS FROM SURFACES [75] Inventor:John A. Smith, Duncan, Okla.

[73] Assignee: Halliburton Company, Duncan,

Okla.

Jan. 29, 1973 21 Appl. No: 327,231

[52] US. Cl 134/3, 134/10, 134/13,

134/41 51 1m. (:1 C23g 1/02 [58] Field of Search 134/3, 13, 41, 10',252/82; 75/101 BE, 117; 423/24; 210/58; 23/312 ME [56] References CitedUNITED STATES PATENTS 2,999,812 9/1961 Krahler 252/855 3,224,873 12/1965Swanson 75/101 R 3,284,501 11/1966 Swanson 260/566 3,294,842 12/1966Swanson 260/566 3,415,616 12/1968 Agers et al.... 423/54 3,428,4492/1969 Swanson 75/117 3,443,887 5/1969 Swanson 423/593 PUMP 3,447,9656/1969 Teumac 252/82 X 3,449,066 6/1969 Swanson 3,464,784 9/1969 Swanson423/63 3,592,775 7/1971 Swanson 252/182 3,655,347 4/1972 Mattison et a175/117 X 3,664,870 5/1972 Oberhofer et a1. 134/3 Primary Examiner-S.Leon Bashore Assistant Examiner-Marc L. Caroff Attorney, Agent, orFirm-John H. Tregoning; Thomas R. Weaver; C. Clark Dougherty, Jr.

[5 7] ABSTRACT Copper deposits are removed from a ferrous metal surfaceby circulating an aqueous acidic solution containing an hydroxycarboxylic acid and/or one of its acidic salts into contact with thesurface, regenerating the spent acid solution by contacting it with animmiscible liquid which preferentially extracts copper dissolved in thesolution, and recon'tacting the surface with the regenerated acidsolution. Subsituted hydroxy benzophenoximes and/0r a-hydroxy oximes areused as the immiscible extraction liquid.

16 Claims, 1 Drawing Figure PUM/ PATENTEL M1019" 3.853.618

PUMP

PUMP

PUMP

PROCESS FOR REMOVING COPPER DEPOSITS PROM SURFACES The present inventionrelates to the removal of copper deposits from surfaces, and moreparticularly, but not by way of limitation, to the removal of waterinsoluble deposits or scale containing copper from metal sur faces bydissolving the deposits in an aqueous acid solution.

In the use and maintenance of industrial equipment the requirement forthe removal of metallic copper or copper containing scale often presentsitself. For example, steam condensers used in conjunction with steamgeneration facilities commonly include surfaces formed of a copper alloywhich are a source of copper metal for the formation of undesirabledeposits on the heat exchange surfaces of the steamgeneration equipment.In steam generation facilitaties associated with electrical powerplants, the deposits which include copper and iron oxides (usuallymagnetite) are commonly formed on steel heat exchange surfaces. In orderto insure the efficient operation of such equipment, the deposits mustperiodically be removed.

A common procedure presently employed for removing copper and iron oxidedeposits from metallic surfaces is to initially contact the surfaceswith an ammoniacal oxidant wash to remove part of the copper depositfollowed by rinsing and the subsequent contact of the surfaces with acleaning solution containing an acid plus a copper complexing material.The copper complexing material functions to tie up the copper so that itis dissolved and held in the cleaning solution. Such multi-stagecleaning procedures are expensive to carry out, and the coppercomplexing materials and cleaning solutions which must be used arecostly.

While strong mineral acid solutions can be used to dissolve depositscontaining copper in a single stage, the dissolved copper readily platesout on surfaces subsequently contacted by the acid solution. By thepresent invention a single stage process for the removal of depositscontaining copper is provided wherein the deposits are removed bydissolution in an aqueous acid solution and retained therein without theaddition of a copper complexing material to the aqueous acid solutionbeing required. In another aspect of the present invention, dissolvedcopper is removed from the aqueous acid solution so that the acidsolution can be readily disposed of in a conventional manner withoutincurring copper poisoning pollution. In a further aspect of the presentinvention a continuous process is provided for the removal of depositscontaining copper or copper and iron oxide wherein the aqueous acidcleaning solution is continuously recycled into contact with the surfaceto be cleaned and dissolved copper is continuously removed from thecleaning solution.

The invention will be further understood from a reading of the followingdescription of preferred embodiments thereof and by the reference to theaccompanying Drawing which is a diagrammatic representation of onesystem which can be used for carrying out the invention.

Broadly stated, the process forthe removal of copper deposits of thepresent invention comprises dissolving the deposits in an aqueoussolution containing an effective quantity of an a-hydroxy carboxylicacid, an acidic salt thereof or a mixture of the acid and acidic saltwherein the acid or salt is represented by the following formula:

wherein R is hydrogen or an alkyl radical having in the range of fromabout 1 to 5 carbon. atoms, R, is hydrogen or a CH COOH radical M ishydrogen, sodium, potassium or ammonium, W is an integer having a valuein the range of from O to 5, and X is an integer having a value in therange of from 0 to 5. Examples of such oz-hydroxy carboxylic acids aregluconic acid, glycolic acid, mucic acid, Z-hydroxy-butanedioic acid andcitric acid. Examples of useful acidic salts of such a-hydroxycarboxylic acids are monoammonium citrate, monosodium gluconate andmonopotassium malate. Aqueous solutions containing an oi-hydroxycarboxylic acid or acidic salt thereof, or mixtures thereof which areuseful in dissolving copper deposits or scale are those wherein thea-hydroxy carboxylic acid, acidic salt or mixture thereof is present inan amount in the range of from about 0.5% by weight of the solution tosaturation. Below a concentration of about 0.5% by weight, the acidsolution is generally ineffective to remove the scale. The scaleremoving effectiveness of the solution increases with increasingconcentrations up to saturation, and the particular concentration useddepends on a variety of factors such as the type equipment to becleaned, the particular type of scale to be removed, and economicfactors.

The aqueous acid solutions described above are particularly suitable forremoving deposits containing cop per and iron oxide from steel surfacesin that both the iron oxide and copperare dissolved by the solution uponcontact therewith. This ability to remove such scale in a single stageprocess is due in part to the capability of the a-hydroxy carboxylicacids or acidic salts thereof to complex or tie up copper ions to alimited degree.

As stated above, a further aspect of the present invention is theremoval of dissolved copper values from the spent aqueous acid solutionso that the acid solution can be readily disposed of and the coppervalues can be recovered if desired. This step is carried out bycontacting the spent aqueous acid solution with a material having theproperty of preferentially extracting copper from low pH aqueoussolutions. Materials which have been found to be suitable for thispurpose are certain oxime derivative compounds which can be adsorbed ona non-reactive solid support such as silica gel or activated charcoal ordissolved in a water immiscible solvent.

Particularly suitable oxime derivative copper extractants for use inaccordance with the process of the present invention are comprised ofa-hydroxy oxime com pounds having the following general formula:

R R and R;, can be any of a variety of organic hydrocarbon radicals suchas aliphatic and alkylaryl radicals and R can also be hydrogen.Preferably, R and R are selected from the group consisting of straightor branched chain alkyl radicals having in the range of from about 6 toabout 20 carbon atoms, and R is hydrogen or a straight or branched chainalkyl radical having in the range of from about 6 to about 20 carbonatoms. a-hydroxy oximes having a total carbon atom content in the rangeof from about 14 to about 40 carbon atoms are preferred. Examples ofsuch compounds are l9-hydroxyhexauriaconta-9,27-dien-l8-oxime;lO-diethyl-8-hydroxytetradecan-7-oxime; and 5,8-diethyl-7-hydroxydodecane-6-oxime.

In addition to the above described a-hydroxy oximes, a class ofsubstituted hydroxy benzophenoximes are also particularly suitable foruse in accordance with the present invention. These compounds have thefollowing basic structure:

In order to impart solubility to the hydroxy benzophenoximes so thatthey can be dissolved in a suitable solvent, they are substituted bysaturated or ethylenically unsaturated aliphatic groups or thecorresponding ether groups. Preferred such compounds are substitutedhydroxy benzophenoximes having the following general formula:

OH NOH R and R can be alike or different and are saturated aliphaticgroups having in the range of from about 1 to 25 carbon atoms, orethylenically unsaturated aliphatic groups having in the range of fromabout 3 to 25 carbon atoms; or R and R are OR groups where R is asaturated aliphatic group having in the range of from about 1 to 25carbon atoms, or an ethylenically unsaturated aliphatic group having inthe range of from 3 to about 25 carbon atoms; and Y and Z are integershaving values in the range of from O to 4. Preferably, the positionortho to the phenolic OI-I substituted carbon atom and the' positionortho to the oxime carbon atom on the other aromatic nucleus areunsubstituted. Branched chain saturated aliphatic hydrocarbonsubstituents are preferred.

Examples of such substituted hydroxy benzophenoximes are2-hydroxy-3-methyl-5 ethylbenzophenoxime; 2-hydroxy-5-( l, l-dimethylpropyl -benzophenoxime; and 2-hydroxy-5-octylbenzophenoxime.

The oxime derivative compounds described above can be utilized inaccordance with the present inven tion for extracting copper from theaqueous acid cleaning solution individually, in mixtures, in the purestate, adsorbed on a non-reactive solid adsorbent, or dissolved in asolvent. When the compounds or mixtures thereof are utilized adsorbed onnon-reactive solid adsorbent, the spent aqueous acid solution containingcopper is flowed through a stationary bed of solid adsorbent so that thecopper is extracted from the solution.

When a solvent for the oxime derivative compounds is used it can bepresent in an amount in the range of from 0 to about 99.5% by weight ofsolution. Preferred solvents for use in accordance with the presentinvention are water immiscible organic solvents. Aliphatic hydrocarbonsolvents such as the petroleum-derived liquid hydrocarbons areparticularly suitable, e.g., kerosene, diesel oil, etc. Various aromaticsolvents may also be used, such as benzene, toluene and xylene. The mostpreferred solvent is kerosene present in the solution containing theoxime derivative extractants in the range of from about by weight toabout 98% by weight of solution.

In carrying out the process of the present invention for the removal ofdeposits containing copper from surfaces, the surfaces can be contactedwith the aqueous solution of an ot-hydroxy carboxylic acid, an acidicsalt thereof or mixtures of the acids and acidic salts described abovein a batch procedure or the acid solution may be continuously circulatedinto contact with the surface for a period of time sufficient todissolve the deposits.

The removal of copper from the spent aqueous acid solution isparticularly advantageous in industrial cleaning applications in thatthe resultant acid solution can be disposed of at the site of thecleaning operation in a conventional manner without incurring copperpoisoning pollution. As indicated previously, the step of removing thecopper from the spent acid solution can be carried out by flowing thesolution into contact with one or more stationary beds of adsorbentmaterial having one or more of the oxime derivative copper extractantsmentioned above adsorbed thereon. Alternatively, the oxime derivativeextractants can be dissolved in a substantially water immiscible organicsolvent of the type described above and the copper extracted from theaqueous acid solution by means of a liquid-liquid extraction step. Whenthe liquid extraction technique is used, the liquid extract solution isstripped of the copper contained therein and reused. The stripping ofthe copper from the extract solution is accomplished by contacting itwith a strong acid. When one or more stationary beds of adsorbentmaterial having the oxime derivative compounds adsorbed thereon areused, the beds are also regenerated by contact with a strong acid.Suitable such acids include aqueous mineral acid solutions such asaqueous sulfuric acid or hydrochloric acid with the acid being presentin the'solution in an amount of from about 2% to about 30% by weight ofsolution. The stripping of the extract solution transfers the copperinto a small volume of aqueous stripping medium which can be processedfurther for the recovery of the copper values if economical, such as bydirect electrolysis, or the relatively small volume solution may betransported to a safe area for the disposal thereof.

Referring now to the drawing, one system which may be used for carryingout the process of the present invention including the removal of copperfrom the aqueous acid cleaning solution by liquid-liquid extraction isillustrated and generally designated by the numeral 10. The system 10 isparticularly suitable for carrying out the process of the invention inindustrial cleaning applications in that the various components of thesystem can be truck or skid mounted for mobility. The system is shownconnected to a steam boiler 12 to be cleaned.

The system 10 includes a conventional liquid-liquid contactor 14 throughwhich the aqueous oz-hydroxy carboxylic acid cleaning solution iscirculated after contacting the surfaces to be cleaned in the boiler 12.That is, the aqueous acid solution is conducted by a conduit 16 from thebottom portion of the contactor 14 to a conventional liquid pump 18.From the discharge of the pump 18, the aqueous acid solution is causedto flow by way of a conduit 20 into and through the boiler 12 so thatthe surfaces having copper deposits or scale thereon are contacted bythe aqueous acid solution. After flowing over the surfaces andcontacting the deposits, the acid solution exits the equipment 12 by wayof a conduit 22 and is conducted to the top portion of the contactor 14.Thus, as will be understood, the aqueous acid solution of the presentinvention is circulated over the surfaces to be cleaned at a rate andfor a time period such that the scale containing copper deposits orcopper and iron oxide deposits is dissolved by the acid solution.

A second conventional liquid-liquid contactor 24 is provided, the topportion of which is connected to the bottom portion of the liquid-liquidcontactor 14 by a conduit 26. A stream of the substantially waterimmiscible extractant liquid described above, i.e., one or more of theoxime derivative extractants dissolved in an organic solvent, is causedto flow from the contactor 24 to the contactor 14. As will beunderstood, the water immiscible liquid extractant is of a density lessthan the aqueous acid cleaning solution so that it flows upwardly withinthe contactor l4'intimately contacting the aqueous acid solution passingdownwardly therein. As the intimate contact takes place between theaqueous phase and organic phase within the contactor 14, copper valuescontained in-the aqueous phase are extracted therefrom into the organicphase. The organic extract solution exits the contactor 14 by way of aconduit28 connected to the top portion thereof and flows to a liquidpump 30. From the pump 30, the organic extract solution passes through aconduit 32 into the bottom portion of the contactor 24 and flowsupwardly therein. A tank of container 34 is provided having a quantityof strong aqueous acid solution therein, and a tank or container 36 isprovided for receiving the acid solution. A conduit 38 connected to thebottom portion of the tank 34 leads a stream of the acid to a pump 40from where it is conducted to the upper portion of the liquid-liquidcontactor 24 by a conduit 42. A conduit 44 is provided connected to thebottom portion of the contactor 24 and to the tank 36.

In operation of the system 10 for removing copper and iron oxidedeposits, the stream of aqueous a-hydroxy carboxylic acid solution iscontinuously circulated over the surfaces of the boiler 12. Thetemperature at which the acid solution contacts the surfaces ispreferably maintained in the range of from about 100F to 200F anddepending upon the atmospheric conditions encountered, a heater (notshown) can be connected into the conduit 20 to control the temperatureof the acid solution at the desired level.

As the aqueous acid solution containing dissolved copper and iron flowsthrough the liquid-liquid contactor 14, it is contacted by the organicextractant solution described above. The organic extractant solution iscontinuously circulated between the contactors l2 and neeringtechniques.

24 so that copper is continuously extracted from the aqueous acidsolution by the organic extractant solution, and copper is continuouslystripped from the extractant solution by the aqueous stripping mediumflowing through the contactor 24. The aqueous acid stripping mediumcontaining stripped copper flows by way of the conduit 44 into the tank36.

As will be understood by those skilled in the art, the flow rates of thevarious streams circulated within the system 10 and through theequipment 12 being cleaned will vary considerably depending upon avariety of factors. For example, the maximum flow rate of aqueous acidcleaning solution circulated through the boiler 12 and contactor 14 isdependent upon the rate of extractant liquid flowing through thecontactor 14 and the time required for separation of the two liquidstreams which in turn is governed by the size of the liquid contactor14. Generally, the optimum size of the equipment used in the system 10,the various flow rates required, etc., are determined using conventionalengi- The pH of the stream of aqueous solution of a-hydroxy carboxylicacid, acidic salt or mixture utilized in accordance with the process ofthe present invention for dissolving copper deposits is preferablymaintained at a level in the range of from about 1.5 to 5. The mostpreferred acid solution pH is in the range of from 2 to 4. The lower pHlimit is dictated by the ability of the oxime derivative compoundsdescribed herein to ex tract copper from the acid solution. Suchextraction can be carried out at an aqueous acid solution pH of as lowas 1.5. The upper pH limit is dictated by the acid solutions ability todissolve the copper deposits. Generally, a pH of 5 or below is required.

Corrosion inhibitors can be added to the aqueous acid cleaning solutionif desired in order to protect the surfaces contacted from acidcorrosion. However, the corrosion inhibitor used should be of a typesuch that it does not cause the organic liquid copper extractant toemulsify. A particularly suitable corrosion inhibitor which can be addedto the aqueous a-hydroxy carboxylic acid or acidic salt solution tominimize corrosion of steel surfaces without causing emulsification ofthe copper extractant solution is a saturated hydrocarbon sulfonatesurface active agent having the chemical formula C H SO Na. Such asurface active agent can be prepared by reacting chlorine with sulfurtrioxide and a hydrocarbon of suitable length in the presence of actiniclight. US. Pat. No. 2,999,812 illustrates a method of preparing such asurface active agent.

ln order to further describe the present invention the followingexamples are given:

EXAMPLE l A laboratory system for carrying out the process of thepresent invention including a horizontal extraction chamber is prepared.A 5% by weight aqueous gluconic acid solution having a pH of about 2 iscirculated through the extraction chamber into contact with a steelsurface having copper and magnetite deposited thereon. The extractionchamber contains a kerosene solution having a mixture of. the oximederivative extractants described above dissolved therein in an amount of10% by weight of solution. Two test runs are made wherein the aqueousacid solution is circulated for 6 hours while being maintained at atemperature of F. At the end of each 6 hour test the copper contents ofthe aqueous acid phase and organic extractant sium or ammonium, W is aninteger having a value in phase are determined. The results of thesetests are the range of from to 5, and X is an integer having a shown 1nTable I below. value in the range of from O to TABLE I Total weight ofVolume of Volume of Copper Content Copper Content Copper OriginallyAqueous Gluconic Organic Extractant of Aqueous of Organic Run Depositedon Acid Solution In Extraction Acid Solution, Extractant Phase,

Test Surface. mg Circulated, ml Chamber, ml mg mg EXAMPLE 2 contactingthe resultant spent aqueous acid solution containing dissolved iron andcopper with a substantially immiscible liquid having the property ofpreferentially extracting at least a portion of dissolved copper fromthe acid solution;

separating the resultant extract liquid containing copper from theextracted aqueous acid solution; and v recirculating the extractedaqueous acid solution into contact with said surfaces.

A second horizontal extraction chamber is added to the laboratory systemdescribed in Example 1 for strip- 1 5 ping the kerosene extractantsolution with a 5% by weight aqueous sulfuric acid solution. Theprocedure of Example 1 is repeated except that the liquid extractantsolution is continuously circulated through the second extractionchamber which contains a quantity of the sulfuric acid strippingsolution. Runs of 6 hours, 5.5 hours and 3 hours are made and the coppercontents of the various aqueous and organic streams determined. Theprocess of claim 1 wherein the said hydroxy The results of these testsare shown in Table II below. carboxylic acid, acidic salt thereof ormixture of acid TABLE ll Total Weight Volume of Volume Duraof CopperAqueous Volume of of Aque- Copper Copper Copper tion Originally GluconicAcid Organic ous Sul- Content Content Content Run of Deposited On ISolution Extractant furic of Aqueous of Organic of Aqueous Test TestSurface, Circulated, Circulated, Acid Gluconic Acid Extractant, SulfuricAcid mg ml ml Used, Solution, mg mg mg 1 6 100 1325 1100 1000 NegligibleNegligible 27.5 2 6 571.1 i360 1100 I000 74.8 Negligible 512.5 3 3 390.51400 1340 800 157.5 Negligible 1 12.5 4 3 534.6 1500 1340 750 120.0Negligible 157.5 5 5.5 569.8 1430 1560 620 93.5 Negligible 248.0

The foregoing examples clearly illustrate the operaand acidic salt ispresent in said aqueous acid solution bility of the process of thepresent invention for the rein an amount in the range of from about 0.5%by weight moval of deposits containing copper and iron oxide. tosaturation.

It is to be understood that the 1nvent1on 1s not to be The process ofclaim 2 wherein Said aqueous acid hmlted to exact detalls of opqatlorfor the solution contains an hydroxy carboxylic acid selected processtechniques shown and described in that mod1f1- from the group consistingof gluconic acid, glycolic canons and equlvalems be readly apparent toacid, mucic acid, 2-hydroxy-butanedioic acid and citric those skilled inthe art, and the invention is to be limacid ited only by the scope ofthe appended claims.

What is claimed is: 1. A process for removing copper and iron oxidedeposits from steel surfaces which consists essentially of:

circulating an aqueous acid solution having a pH in the range of about1.5 to about 5 and containing an 4. The process of claim 2. wherein saidaqueous acid solution contains an acidic salt of an hydroxy carboxylicacid selected from the group consisting of monoammonium citrate,monosodium gluconate and monopotassium malate.

hy r xy carb xyl acid, an acidic Salt 0f said 11- 5. The process ofclaim 2 wherein said substantially droxy carboxylic acid or a mixture ofsaid acids and imrniscible liquid having the property of preferentiallysalts into contact with said surfaces so that the copextracting copperis selected from the group consisting per and iron oxide deposits aredissolved therein, f;

said hydroxy carboxylic acid or acidic salt thereof an i /d li h i oximeh i h general f having the general formula: mula:

. 6 whereln R is hydrogen or an alkyl radical having 1n the 5 wherein Rand R are selected from the group consistrange of from i to 5 carbonatoms, R is hydrogen or ing of straight or branched chain alkyl radicalshaving a CH COOH radical, is hydrogen, sodium, potasin the range of fromabout 6 to about 20 carbon atoms O11 NOI-I QM-Q wherein R and R arealike or different and are saturated aliphatic groups having in therange of from about 3 to 25 carbon atoms, or R and R comprise OR groupswhere R is a saturated aliphatic group having in the range of from about1 to 25 carbon atoms or an ethylenically unsaturated group having in therange of from about 3 to carbon atoms, Y and Z are integers havingvalues in the range of from O to 4, but both Y and Z are not 0; and

mixtures of the foregoing compounds.

6. The process of claim 5 wherein said substantially 25 i immiscibleliquid having the property of preferentially extracting copper isfurther characterized to include a water immiscible organic solvent forsaid a-hydroxy aliphatic oximes, substituted hydroxy benzophenoximes ormixtures thereof, said organic solvent being present in an amount in therange of from 0 to about 99.5% by weight of solution.

7. The process of claim 6 which is further characterized to include thestep of removing copper from the 3 separated extract liquid containingcopper.

8. The process of claim 7 wherein the step of removing copper from theextract liquid comprises contacting said liquid with an aqueous acidsolution so that copper is stripped therefrom.

9. A process for removing a copper deposit from a ferrous metal surfaceconsisting essentially of:

a first step of contacting said copper deposit with an aqueous solventtherefore to thereby produce a copper-containing solvent solution,

a second step of contacting said copper-containing solvent solution in afirst solvent extraction zone with a substantially immiscible liquidhaving pref erence for copper to remove at least a portion of saidcopper from said coper-containing solvent so lution to thereby produce afirst extract phase consisting essentially of said substantiallyimmiscible liquid and copper and a first raffinate phase consistingessentially of said aqueous solvent,

a third step of separating said first extract phase from said firstraffinate phase, and

a fourth step of contacting said copper deposit with said firstraffinate phase,

wherein said aqueous solvent is an aqueous solution containing anhydroxy carboxylic acid, an acidic salt of an hydroxy carboxylic acid ora mixture of said acids and salts, the hydroxy carboxylic acid or acidicsalt thereof having the general formula wherein R is hydrogen or analkyl radical having in the range of from 1 to 5 carbon atoms, R, ishydrogen or a -CH COOH radical, M is hydrogen, sodium, potas sium orammonium, W is an integer having a value in the range of from 0 to 5,and X is an integer having a value in the range of from 0 to 5; furtherwherein said substantially immiscible liquid is selected from the groupconsisting of an oz-hydroxy oxime having the general formula wherein Rand R are selected from the group consisting of straight or branchedchain alkyl radicals having in the range of from about 6 to about 20carbon atoms and R is hydrogen or a straight or branched chain alkylradical having in the range of from about 6 to about 20 carbon atoms,

a substituted hydroxy benzophenoxime having the general formula OII NOllwherein R and R are alike or different and are satumixtures of theforegoing compounds; and still further wherein said first step and saidsecond step are conducted at a pH in the range of from about 1.5 toabout 5 and at a temperature in the range of from about F to about 200F.

10. The process of claim 9 further including a fifth step of contactingsaid first extract phase in a second solvent extraction zone with anaqueous in-' organicacid having preference for copper to remove saidcopper from said first extract phase to thereby produce a secondraffinate phase consisting essentially of said immiscible liquid, and asecond extract phase consisting essentially of said copper dissolved insaid aqueous inorganic acid,

a sixth step of separating said second extract phase from said secondraffinate phase, and

a seventh step of contacting said copper-containing solvent solution insaid first solvent extraction zone I with said second raffinate phase.11. The process of claim 10 wherein said inorganic acid is a mineralacid and is present in an amount in the range of from about 2% to about30% by weight of solution.

12. The process of claim 9 wherein said hydroxy carboxylic acid, acidicsalt thereof or mixture of acid and acidic salt is present in saidaqueous solvent in an amount in the range of from about 0.5% by weightto saturation.

13. The process of claim 12 wherein said hydroxy carboxylic acid isselected from the group consisting of gluconic acid, glycolic acid,mucic acid, 2-hydroxybutanedioic acid and citric acid.

14. The process of claim 12 wherein said acidic salt of said hydroxycarboxylic acid is selected from the group consisting of monoammoniumcitrate, monosodium gluconate and monopotassium malate.

16. The process of claim 15 wherein said water immiscible organicsolvent is kerosene present in an amount in the range of from about toabout 98%

1. A PROCESS FOR REMOVING COPPER AND IRON OXIDE DEPOSITS FROM STEELSURFACES WHICH CONSISTS ESSENTIALLY OF: CIRCULATING AN AQUEOUS ACIDSOLUTION HAVING A PH IN THE RANGE OF ABOUT 1.5 TO ABOUT 5 AND CONTAININGAN HYDROXY CARBOXYLIC ACID, AN ACIDIC SALT OF SAID HYDROXY CARBOXYLICACID OR A MIXTURE OF SAID ACIDS AND SALTS INTO CONTACT WITH SAIDSURFACES SO THAT THE COPPER AND IRON OXIDE DEPOSITS ARE DISSOLVEDTHEREIN, SAID HYDROXY CARBOXYLIC ACID OR ACIDIC SALT THEREOF HAVING THEGENERAL FORMULA:
 2. The process of claim 1 wherein the said hydroxycarboxylic acid, acidic salt thereof or mixture of acid and acidic saltis present in said aqueous acid solution in an amount in the range offrom about 0.5% by weight to saturation.
 3. The process of claim 2wherein said aqueous acid solution contains an hydroxy carboxylic acidselected from the group consisting of gluconic acid, glycolic acid,mucic acid, 2-hydroxy-butanedioic acid and citric acid.
 4. The processof claim 2 wherein said aqueous acid solution contains an acidic salt ofan hydroxy carboxylic acid selected from the group consisting ofmonoammonium citrate, monosodium gluconate and monopotassium malate. 5.The process of claim 2 wherein said substantially immiscible liquidhaving the property of preferentially extracting copper is selected fromthe group consisting of: an Alpha -hydroxy aliphatic oxime having thegeneral formula:
 6. The process of claim 5 wherein said substantiallyimmiscible liquid having the property of preferentially extractingcopper is further characterized to include a water immiscible organicsolvent for said Alpha -hydroxy aliphatic oximes, substituted hydroxybenzophenoximes or mixtures thereof, said organic solvent being presentin an amount in the range of from 0 to about 99.5% by weight ofsolution.
 7. The process of claim 6 which is further characterized toinclude the step of removing copper from the separated extract liquidcontaining copper.
 8. The process of claim 7 whErein the step ofremoving copper from the extract liquid comprises contacting said liquidwith an aqueous acid solution so that copper is stripped therefrom.
 9. Aprocess for removing a copper deposit from a ferrous metal surfaceconsisting essentially of: a first step of contacting said copperdeposit with an aqueous solvent therefore to thereby produce acopper-containing solvent solution, a second step of contacting saidcopper-containing solvent solution in a first solvent extraction zonewith a substantially immiscible liquid having preference for copper toremove at least a portion of said copper from said coper-containingsolvent solution to thereby produce a first extract phase consistingessentially of said substantially immiscible liquid and copper and afirst raffinate phase consisting essentially of said aqueous solvent, athird step of separating said first extract phase from said firstraffinate phase, and a fourth step of contacting said copper depositwith said first raffinate phase, wherein said aqueous solvent is anaqueous solution containing an hydroxy carboxylic acid, an acidic saltof an hydroxy carboxylic acid or a mixture of said acids and salts, thehydroxy carboxylic acid or acidic salt thereof having the generalformula
 10. The process of claim 9 further including a fifth step ofcontacting said first extract phase in a second solvent extraction zonewith an aqueous inorganic acid having preference for copper to removesaid copper from said first extract phase to thereby produce a secondraffinate phase consisting essentially of said immiscible liquid, and asecond extract phase consisting essentially of said copper dissolved insaid aqueous inorganic acid, a sixth step of separating said secondextract phase from said second raffinate phase, and a seventh step ofcontacting said copper-containing solvent solution in said first solventextraction zone with said second raffinate phase.
 11. The process ofclaim 10 wherein said inorganic acid is a mineral acid and is present inan amount in the range of from about 2% to about 30% by weight ofsolution.
 12. The process of claim 9 wherein said hydroxy carboxylicacid, acidic salt thereof or mixture of acid and acidic salt is presentin said aqueous solvent in an amount in the range of from about 0.5% byweight to saturation.
 13. The process of claim 12 wherein said hydroxycarboxylic acid is selected from the group consisting of gluconic acid,glycolic acid, mucic acid, 2-hydroxy-butanedioic acid and citric acid.14. The process of claim 12 wherein said acidic salt of said hydroxycarboxylic acid is selected from the group consisting of monoammoniumcitrate, monosodium gluconate and monopotassium malate.
 15. The processof claim 13 wherein said substantially immiscible liquid havingpreference for copper is further characterized to include a waterimmiscible organic solvent for said Alpha -hydroxy aliphatic oximes,substituted hydroxy benzophenoximes or mixtures thereof, said organicsolvent being present in an amount in the range of from 0 to about 99.5%by weight of solution.
 16. The process of claim 15 wherein said waterimmiscible organic solvent is kerosene present in an amount in the rangeof from about 80% to about 98% by weight of solution.